Ammonium nitrate slurry sensitized with nitro substituted alkanols



United States Patent 3,275,485 AMMONIUM NITRATE SLURRY SENSITIZED WITH NlTRO SUBSTITUTED ALKANOLS Richard S. Egly, West Terre Haute, Ind, assignor to Commercial Solvents Corporation, a corporation of Maryland No Drawing. Filed July 30, 1964, Ser. No. 386,421

4 Claims. (Cl. 149-47) The present invention relates to new high-density ammonium nitrate slurry compositions suitable for use as explosives and for making explosives and is particularly concerned with certain nitro substituted alkanol-containing ammonium nitrate slurry compositions.

Ammonium nitrate has long been known to be flammable and explosive and these properties have been made use of extensively, ammonium nitrate-oil mixtures being now widely used as an explosive although they possess certain inherent disadvantages such as low density and rela tive insensitivity when used as an explosive.

While these low density ammonium nitrate explosives are satisfactory for certain situations involving relatively easy blasting, they cannot develop the detonation velocities and bore hole pressures needed in blasting hard rock diflicult to fracture. The ammonium compositions of the present invention are of relatively high density, ranging from 1.1 to 1.6, and are sufliciently sensitive for practical application in blasting without using any ingredient more hazardous than ammonium nitrate or any manufacturing steps not readily, simply and safely performed at the site. High density ammonium nitrate mixtures of this range used in the past have either involved a sensitizer, e.g. trinitrotoluene, more sensitive and dangerous to handle than the ammonium nitrate and hence such mixtures were diificult to store, ship, handle and mix with other ingredients or they involved manufacturing steps difiicult to carry out in the field.

It is extremely dangerous to prepare ammonium nitrate explosives containing trinitrotoluene or other similar explosives outside of a permanent industrial explosives factory meeting all known safety requirements and operated by personnel experienced in the manufacture of explosives. Furthermore, the ammonium nitrate and carbonaceous material ordinarily used therewith must be thoroughly mixed and combined in equipment which is only found in an industrial plant for the manufacture of explosives. As large amounts of ammonium nitrate and sensitizers are always present in factory operations, there is the ever-present danger of disastrous explosions which may demolish the area surrounding the industrial plant for the production of explosives.

Ammonium nitrate slurry explosives have attracted significant interest. These slurry compositions generally contain the ammonium nitrate as an oxidizer, trinitrotoluene, smokeless powder and other sensitizing materials as a sensitizer, and about 15 to 25 percent water. They may also contain optional additives such as thickeners, e.g. gu-ar gum. These slurry compositions function well however, significant amounts of water, eg about 20 percent, are generally required to provide a composition of high density. Water in large amounts is undesirable since it is a desensitizer and also removes energy from the explosive, i.e. it provides gas by absorption of a large amount of heat and at the expense of lower detonation temperatures.

It has now been surprisingly discovered that ammonium nitrate slurry compositions can be provided which contain relatively small amounts of water but are of high density and provide higher temperatures, pressure and more powerful explosions. Maximum densities are achieved with a minimum amount of Water. For instance, densities which formerly required from about 15 to 20 percent water can be achieved using about 5 percent water in the present composition which composition is also superior as an explosive.

The ammonium nitrate compositions of the present invention which have generally about 10 to 50% by weight of a nitro substituted alkanol and about 2 to 10% by weight water can be advantageously employed either as explosives or in the preparation of explosives. Compositions containing up to about 6%, preferably about 3 to 6% by weight water and about 15 to 30%, preferably 15 to 25 nitro substituted alkanol with the balance ammonium nitrate provide particularly effective explosives and are generally more effective as such than other known ammonium nitrate explosives as noted supra. As the amount of said nitro compound and/ or water are increased beyond 25% by weight and 6% respectively, the sensitivity of the composition as an explosive decreases. The nitro compounds were surprisingly found capable of greatly increasing the amount of the liquid phase and thereby the density of the slurry, while at the same time performing the functions of a sensitizer, providing fuel for the explosive, and providing extra energy from the nitro group which they contain. The nitro substituted alkanols are safe and, accordingly, as they serve as sensitizers, the use of explosives as sensitizers, e.g. TNT, which are dangerous to handle are obviated. Thus the compositions of the present invention containing little water can have ammonium nitrate as the most sensitive component and yet they can be eifectively utilized in explosive systems. Known ammonium nitrate slurries containing greater amounts of water necessarily use sensitizers such as trinitrotoluene which are dangerous to handle.

The compositions of the present invention can be prepared using any order of mixing the components. Advantageously they can be prepared by making a solution with the nitro compound and water components and, while stirring the solution, adding the ammonium nitrate to it. A particularly suitable slurry comprises about 3 parts of ammonium nitrate and 1 part of the solution. Both the nitro compound and the ammonium nitrate dissolve in the water to provide a substantial amount of solution of high density without very much water. Moreover, the composition can be easily prepared at the site of use. Alternatively, the explosives, in many instances, can be prepared directly in the bore hole by simply placing a solution of the nitro compound and water in the bore hole and adding the ammonium nitrate in an amount and concentration which gives a final composition having the water and nitro compound content that provides the desired high degree of sensitivity.

The compositions of the present invention can, 01 course, include optional additives such as carbon black, ground coal, morpholine, lower alkyl alcohols, dimethylformamide, dimethylsulfamide, aluminum, sulfur, ferrosilicon, parafl'in wax, thickeners, e.g. guar gum, resin or other ingredients ordinarily incorporated into ammonium nitrate explosive compositions.

The ammonium nitrate utilized in my invention for explosives is preferably essentially anhydrous, pure ammonium nitrate or fertilizer grade ammonium nitrate, either uncoated or coated with various coating agents such as resin, diatomaceous earth, etc. Pure anhydrous ammonium nitrate is preferred. The nitro substituted alkanols used in the compositions of the present invention are soluble in water and have the formula where R is hydrogen, lower alkyl or lower hydroxyalkyl 1nd R is lower alkyl or lower hydroxyalkyl. Suitable :ompounds include 2-nitro-l,3-propanediol; 2-nitro-2- nethyl 1,3 propanediol; 2 nitro 2 ethyl 1,3- propanediol, 2-nitr-o-2-methyl-propano1; and 2-nitro-2- :thyl-propanol, however, the preferred compound is tris- (hydroxymethyl)-nitromethane.

The compositions of the invention require primer charges to initiate and propagate detonation waves through the charge. If the bore hole in which the explosive is to be detonated is wet, horizontal or slanted, the ammonium nitrate charge can be placed in a container such as a polyethylene bag and the water-nitro compound or water-nitro compound-ammonium nitrate solution introduced into the container or cartridge just prior to its insertion in the bore hole.

The following examples will illustrate a method for preparing the explosive composition of the present invention and use of the compositions.

Example I 1668.5 gms. of ammonium nitrate (AN) were added to 715 gms. of water to provide a solution composed of 70% ammonium nitrate and 30% water. 2935.0 gms. of tris(hydroxymethyl)nitromethane (TN) was added to this solution while heating to 40 C. to effect dissolution of all of the nitro compounds. On cooling to room temperature the solution remained clear. This solution, composed of 13.44% water, 31.37% ammonium nitrate, and 5 5.18% tris(hydroxymethyl)nitromethane was mixed with 23 pounds (10,433 gms.) of mesh high'density, uncoated ammonium nitrate fines and the resulting slurry which was composed of about 76.4 wt. percent AN, 19.1% TN and 4.5% water was packaged in 5" x 36", 6 mil polyethylene package. The density of the mixture was found to be approximately 1.17. At the testing site the polyethylene bag was buried in soil so that the top of the bag was level with the surface of the ground. Two blocks of Procore booster explosive were taped to the top of the bag. Two electric dynamite caps were pressed into holes in the Procore block. The caps were then fired to initiate the Procore blocks and the latter in turn detonated the ammonium nitrate-nitro com pound-water composition. A crater which was about 20 feet in diameter and three feet deep was formed.

Examples IlVI Similar explosives can be produced by employing the general procedure of Example I and employing instead of tris(hydroxymethyl)nitromethane the following:

II. 2-nitro-l,3-propanediol.

III. 2-nitro-2-methyl-1,3-propanediol. IV. 2-nitro-2-ethyl-1,3-propanediol. V. 2-nitro-2-methyl-propanol.

VI. 2-nitro-2-ethyl-propanol.

Example VII A slurry composed of 51 weight percent ammonium nitrate, 40 weight percent tris(hydroxymethyl)nitromethane (TN) and 9 weight percent Water was mixed to a fluid consistency over a three hour period. A weight of uncoated ammonium nitrate equal to that of the initial slurry was added to the slurry to provide a resulting composed of 75.5 weight per-cent ammonium nitrate, 20 weight percent TN and 4.5 weight percent water. This slurry was mixed overnight to a uniform consistency. The density of the slurry was determined by measuring the volume and weight of the slurry in a 2-liter graduated cylinder. The initial volume of 1,931 grams of slurry was found to be 1,380 ml. giving a bulk density of 1.40. Evacuation of the graduate caused evolution of air entrapped in the slurry reducing the volume to 1260 ml. when measured at atmospheric pressure. The bulk density of this slurry is 1.53.

It is claimed:

1. Ammonium nitrate slurry compositions suitable for use in the explosive art consisting essentially of ammonium nitrate, about 2 to 10% by weight water, and about 10 to by weight of 2. nitro compound having the formula where R is selected from the group consisting of hydrogen, lower alkyl and lower hydroxyalkyl and R' is selected from the group consisting of lower alkyl and lower hydroxyalkyl.

2. Ammonium nitrate compositions suitable for use as explosives consisting essentially of ammonium nitrate, about 2 to 10% by weight water and about 10 to 50% by weight of tris(hydroxymethyl)nitromethane.

3. Ammonium nitrate compositions suitable for use in producing explosives consisting essentially of ammonium nitrate, about 3 to 6% by weight water and about 15 to 25% by weight tris(hydroxymethyl)nitromethane.

4. The composition of claim 1 wherein it contains about 3 to 6% by weight water and about 15 to 25% by weight of the nitro compound.

References Cited by the Examiner UNITED STATES PATENTS 3,161,551 12/1964 Egly et a1. 149-47 X BENJAMIN R. PADGETT, Acting Primary Examiner.

S. J. LECHERT, Assistant Examiner. 

1. AMMONIUM NITRATE SLURRY COMPOSITIONS SUITABLE FOR USE IN THE EXPLOSIVE ART CONSISTING ESSENTIALLY OF AMMONIUM NITRATE, ABOUT 2 TO 10% BY WEIGHT WATER, AND ABOUT 10 TO 50% BY WEIGHT OF A NITRO COMPOUND HAVING THE FORMULA 